Electroconductive belts are widely used for the transport of goods that should not be exposed to the discharge of static electricity. Such products may include electronic devices and other kinds of goods that may be damaged due to exposure to static electricity. Another application where static electricity is undesirable is people mover belts. With the use of conductive materials, static electricity can be discharged through the belt to the metal frame of the machine.
Industrial standards such as EN 61340 define the requirements for conductive materials and applications, as they relate to the discharge of static electricity. The required level of conductivity may vary for different industrial applications. A typical electrical resistance for materials suitable for the dissipation of static electricity is 102-105 Ω(Ohm). Unfortunately, belts produced from electroconductive materials such as electroconductive polyacetal or electroconductive polypropylene are very expensive. Costs of such materials may range from two to three times the cost of standard plastic materials. The plastic compounds usually contain stainless steel fibers, carbon black fibers, or powders to make them conductive.
In order to reduce the cost, it is common to assemble modular belts in a bricklayed module pattern by combining standard plastic modules with electroconductive modules. The distance between the electroconductive modules must be small enough to always guarantee contact inside the surface size of a standard shoe. For belt modules having a small pitch, it is not difficult to position the modules to meet this requirement. Various patterns for mixing the electroconductive modules with standard plastic modules are possible. Referring to FIG. 1, an example of a prior art bricklayed belt 10 for a people mover application includes standard modules 13 and electroconductive modules 16. The footprints 19 of the user contact at least one electroconductive module 16 to dissipate the static electricity. This type of belt is lower in cost than a belt constructed of all electroconductive modules, but the belt may still be expensive for some applications. For larger module sizes (e.g., belts having pitches equal or larger than two inches), mixed module patterns as described above need a more dense arrangement of the electroconductive modules, which increases the cost of the belt. Accordingly, there is a need for a solution that guarantees sufficient electroconductivity at a lower cost.